In the paint industry, stock control and logistics are rationalised by using colour mixing systems. In such systems, a paint colour selected for a customer is produced by selecting a base paint from a range of available base paints and adding to the selected base paint one or more pigment pastes which are intimate mixtures of one or more pigments with paste resins which latter having good dispersing properties. Such systems have been widely used in the field of decorative coatings, as disclosed, e.g., in EP 0 311 209 A1.
Examples of pigment pastes for paint tinting systems are disclosed in WO 91/06607 A1 (water-borne polyesters), WO 99/49963 A1 (solvent-borne polyesters), and EP 0 458 479 A2 (acrylic modified polyesters for solvent-borne paints). In addition to at least one pigment, pigment pastes typically include special resins, solvents, and usually also additives. Pigments for various colours vary considerably in chemical nature, from simple inorganic elements such as carbon in the form of channel black or lamp black, to inorganic oxides (such as iron oxides, copper, cobalt, chromium and lead based pigments) and organic pigments (such as azo pigments, phthalocyanine pigments, and polycyclic aromatic pigments such as perylene, anthraquinone and quinacridone pigments). For each pigment, a compatible resin needs to be used. This resin needs, in turn, to be compatible with the binder system of the base paints and with the resins used in other pigment pastes as well, since for most colours, the addition of more than one pigment paste is required. The resin should also be able to disperse a sufficient amount of the pigment. Up to now it has not been possible to use tinting systems compatible with both solvent borne paints and water borne paints, and which are also compatible with the usual range of binder resins.